In order to promote the milk flow from the teatcup to a milk receiving unit, gas is commonly supplied to the milk flow. The general purpose of the gas supply, for instance in the form of a flow of air to the milk flow, is thus to create an efficient and a uniform milk flow from the teatcup to the milk receiving unit. Traditionally, the supply of gas took place via the so called teatcup claw. In quarter milking, it is known to supply the gas via the teatcup, for instance into a milk space created beneath the teat. However, the supply of gas into the milk space is an area of some concern.
SE-L-0002401-8 discloses a teatcup of the kind initially defined, which comprises a sleeve, a teatcup liner provided in the sleeve and a milk receptacle comprising a milk space. An inlet channel extends between an inner space of the teatcup liner and the milk space for conveying milk from a teat of an animal to be milked into the milk space. An outlet channel extends from the milk space and is formed by a first nipple connected to a milk conduit for conveying the milk in a milk flow from the milk space. A valve member is provided for conveying air into the milk space for promoting the milk flow. The air passes the valve member straight into the milk space directly from outside the teatcup.
A teatcup, similar to the one of SE-L-0002401-8, is disclosed in EP-566 977. The teatcup disclosed in this document comprises a valve housing at the lower end. The valve housing forms a milk space beneath the teat. An air aperture extends through the wall of the valve housing.
Investigations performed by the applicant have shown that high vacuum variations may occur at the teat tip in the milk space in teatcups of this kind and that the evacuation of the milk may be poor during high milk flow conditions. It is believed that these problems may be overcome by creating a large volume of the milk space beneath the teat. However, the investigations also show that such a large volume is not sufficient in order to eliminate the problems.
Moreover, air supplied to the milk flow, for instance via the milk space, may be detrimental to the quality of the milk, in particular if there is a jet of air hitting the milk contained in the milk space.
A further problem is that the air, where the milking takes place in the immediate vicinity of the animal may be contaminated, and thus not suitable for being mixed with the milk.